Compressor diagnostic and protection system and method

ABSTRACT

A system and method includes a compressor operable in a refrigeration circuit and including a motor, a current sensor providing a high-side signal indicative of an operating condition of a high-pressure side of the refrigeration circuit, a discharge line temperature sensor providing a low-side signal indicative of an operating condition of a low-pressure side of the refrigeration circuit, and processing circuitry processing the high-side signal and the low-side signal to indirectly determine a non-measured operating parameter of the refrigeration circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/059,646 filed on Feb. 16, 2005, which claims the benefit of U.S.Provisional Application No. 60/565,795, filed on Apr. 27, 2004. Thedisclosure of the above application is incorporated herein by reference.

FIELD

The present teachings relate to compressors, and more particularly, toan improved diagnostic system for use with a compressor.

BACKGROUND

Compressors may be used in a wide variety of industrial and residentialapplications to circulate refrigerant within a refrigeration, heat pump,HVAC, or chiller system (generically “refrigeration systems”) to providea desired heating or cooling effect. In any of the foregoingapplications, the compressor should provide consistent and efficientoperation to ensure that the particular application (i.e.,refrigeration, heat pump, HVAC, or chiller system) functions properly.

Residential air conditioning and refrigeration systems may include aprotection device that intermittently trips the system, which will causediscomfort to a homeowner, eventually resulting in a visit to the homeby a serviceperson to repair a failure in the system. The protectiondevice may shut down the compressor when a particular fault or failureis detected to protect the compressor from damage. In addition,protection devices may also detect a pressure within the compressor orbetween the compressor and associated system components (i.e.,evaporator, condenser, etc.) in order to shut down the compressor toprevent damage to both the compressor and system components if pressurelimits are exceeded.

The types of faults that may cause protection concerns includeelectrical, mechanical, and system faults. Electrical faults have adirect effect on the electrical motor in the compressor while mechanicalfaults generally include faulty bearings or broken parts. Mechanicalfaults often raise the internal temperature of the respective componentsto high levels, thereby causing malfunction of, and possible damage to,the compressor.

System faults may be attributed to system conditions such as an adverselevel of fluid disposed within the system or to a blocked flow conditionexternal to the compressor. Such system conditions may raise an internalcompressor temperature or pressure to high levels, thereby damaging thecompressor and causing system inefficiencies or failures. To preventsystem and compressor damage or failure, the compressor may be shut downby the protection system when any of the aforementioned conditions arepresent.

Conventional protection systems typically sense temperature and/orpressure parameters as discrete switches and interrupt power supply tothe motor should a predetermined temperature or pressure threshold beexperienced. Parameters that are typically monitored in a compressorinclude the temperature of the motor winding, the temperature of thespiral wraps or scrolls (for a scroll-type compressor), the pressure atdischarge, the electrical current going to the motor, and a continuousmotor overload condition. In addition, system parameters such as a fanfailure, loss of charge, or a blocked orifice may also be monitored toprevent damage to the compressor and system. A plurality of sensors aretypically required to measure and monitor the various system andcompressor operating parameters. Typically, each parameter measuredconstitutes an individual sensor, thereby creating a complex protectionsystem in which many sensors are employed.

The most common protection arrangements for residential refrigerationsystems employ high/low pressure cutout switches and a plurality ofsensors to detect individual operating parameters of the compressor andsystem. The sensors produce and send a signal indicative of compressorand/or system operating parameters to processing circuitry so that theprocessing circuitry may determine when to shut down the compressor toprevent damage. When the compressor or system experiences an unfavorablecondition, the processing circuitry directs the cutout switches to shutdown the compressor.

Sensors associated with conventional systems are required to quickly andaccurately detect particular faults experienced by the compressor and/orsystem. Without a plurality of sensors, conventional systems wouldmerely shut down the compressor when a predetermined threshold load orcurrent is experienced, thereby requiring the homeowner or servicepersonto perform many tests to properly diagnose the cause of the fault priorto fixing the problem. In this manner, conventional protection devicesfail to precisely indicate the particular fault and therefore cannot beused as a diagnostic tool.

SUMMARY

A system includes a compressor operable in a refrigeration circuit andincluding a motor, a current sensor providing a high-side signalindicative of an operating condition of a high-pressure side of therefrigeration circuit, a discharge line temperature sensor providing alow-side signal indicative of an operating condition of a low-pressureside of the refrigeration circuit, and processing circuitry processingthe high-side signal and the low-side signal to indirectly determine anon-measured operating parameter of the refrigeration circuit.

A method includes generating a high-side signal indicative ofhigh-pressure operating conditions at a compressor in a refrigerationcircuit, generating a low-side signal indicative of low-pressureoperating conditions at the compressor in the refrigeration circuit, andprocessing the high-side signal and the low-side signal to indirectlydetermine a non-measured operating parameter of the refrigerationcircuit.

Further areas of applicability of the present teachings will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, areintended for purposes of illustration only and are not intended to limitthe scope of the teachings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a compressor in accordance with theprinciples of the present teachings;

FIG. 2 is a cross-sectional view of the compressor of FIG. 1incorporating a protection system in accordance with the principles ofthe present teachings;

FIG. 3 is a cross-sectional view of the compressor of FIG. 1incorporating a protection system in accordance with the principles ofthe present teachings;

FIG. 4 is a cross-sectional view of a compressor incorporating aprotection system in accordance with the present teachings;

FIG. 5 is a graphical representation of discharge superheat versussuction superheat;

FIG. 6 is a graphical representation showing discharge line temperaturedue to increased suction temperature;

FIG. 7 is a graphical representation showing that an increased dischargeline temperature reflects a fast decline in suction pressure;

FIG. 8 is a graphical representation showing three phases of compressoroperation; start-up, quasi-steady state, and steady state;

FIG. 9 is a schematic representation of the protection system of FIG. 2;

FIG. 10 is a flow-chart depicting a high-side control algorithm for theprotection system of FIG. 9;

FIG. 11 is a flow-chart depicting a low-side control algorithm for theprotection system of FIG. 9;

FIG. 12 is a graphical representation of a low-side sensor response asrepresented by the compressor discharge line temperature under a normalcondition versus a low-refrigerant charge condition;

FIG. 13 is a graphical representation of how other fault modes could bedifferentially detected by a discharge line temperature sensor withinthe first 30-60 second period versus longer time periods aftercompressor start up;

FIG. 14 is a graphical representation of a high-side fault based on thevalue of measured current being relatively higher than nominal;

FIG. 15 is a graphical representation of operating modes for acompressor;

FIG. 16 is schematic of the compressor of FIG. 1 incorporated into aheat pump system;

FIG. 17 is a schematic representation of an efficiency-monitoring systemincorporated into a network;

FIG. 18 is a flowchart representing a fault tree for use with theprotection system of FIG. 9;

FIG. 19 is a graphical representation of compressor power versuscondensing temperature;

FIG. 20 is a graphical representation of discharge line temperatureversus evaporator temperature;

FIG. 21 is a graphical representation of compressor mass flow versusdischarge line temperature;

FIG. 22 is a flowchart detailing a compressor capacity and efficiencyalgorithm;

FIG. 23 is a graphical representation of compressor capacity versuscondenser temperature;

FIG. 24 is a graphical representation of compressor power versus ambienttemperature;

FIG. 25 is a graphical representation of compressor efficiency versuscondenser temperature;

FIG. 26 is a graphical representation of percentage condensertemperature difference versus percent capacity;

FIG. 27 is a schematic representation of a high-side diagnostic based oncondenser temperature difference;

FIG. 28 is a schematic representation of a low-side diagnostic based ondischarge superheat;

FIG. 29 is a flowchart for a compressor installation;

FIG. 30 is a flow-chart of an efficiency-monitoring system in accordancewith the principles of the present teachings;

FIG. 31 is a graphical representation of discharge line temperatureminus ambient temperature versus ambient temperature for use with thecompressor installation procedure of FIG. 29; and

FIG. 32 is a graphical representation of current versus ambienttemperature for use with the compressor installation procedure of FIG.29.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is in no wayintended to limit the present teachings, its application, or uses.

With reference to the drawings, a compressor 10 includes a compressorprotection and control system 12 for determining an operating mode forthe compressor 10 based on sensed compressor parameters to protect thecompressor 10 by limiting operation when conditions are unfavorable. Theprotection and control system 12 toggles the compressor betweenoperating modes including a normal mode, a reduced-capacity mode, and ashutdown mode. The compressor 10 will be described and shown as a scrollcompressor but it should be understood that any type of compressor maybe used with the protection and control system 12. Furthermore, whilethe compressor 10 will be described in the context of a refrigerationsystem 11, compressor 10 may similarly be incorporated into other suchsystems such as, but not limited to, a heat pump, HVAC, or chillersystem.

With particular reference to FIGS. 1-4, the compressor 10 is shown toinclude a generally cylindrical hermetic shell 14 having a welded cap 16at a top portion and a base 18 having a plurality of feet 20 welded at abottom portion. The cap 16 and base 18 are fitted to the shell 14 suchthat an interior volume 22 of the compressor 10 is defined. The cap 16is provided with a discharge fitting 24, while the shell 14 is similarlyprovided with an inlet fitting 26, disposed generally between the cap 16and base 14, as best shown in FIGS. 2-4. In addition, an electricalenclosure 28 is fixedly attached to the shell 14 generally between thecap 16 and base 18 and operably supports a portion of the protectionsystem 12 therein, as will be discussed further below.

A crankshaft 30 is rotatively driven by an electric motor 32 relative tothe shell 14. The motor 32 includes a stator 34 fixedly supported by thehermetic shell 14, windings 36 passing therethrough, and a rotor 38press fitted on the crankshaft 30. The motor 32 and associated stator34, windings 36, and rotor 38 are operable to drive the crankshaft 30relative to the shell 14 to thereby compress a fluid.

The compressor 10 further includes an orbiting scroll member 40 having aspiral vane or wrap 42 on the upper surface thereof for use in receivingand compressing a fluid. An Oldham coupling 44 is positioned betweenorbiting scroll member 40 and a bearing housing 46 and is keyed toorbiting scroll member 40 and a non-orbiting scroll member 48. TheOldham coupling 44 transmits rotational forces from the crankshaft 30 tothe orbiting scroll member 40 to thereby compress a fluid disposedbetween the orbiting scroll member 40 and non-orbiting scroll member 48.Oldham coupling 44 and its interaction with orbiting scroll member 40and non-orbiting scroll member 48 is preferably of the type disclosed inassignee's commonly-owned U.S. Pat. No. 5,320,506, the disclosure ofwhich is incorporated herein by reference.

Non-orbiting scroll member 48 also includes a wrap 50 positioned inmeshing engagement with wrap 42 of orbiting scroll member 40.Non-orbiting scroll member 48 has a centrally disposed discharge passage52 which communicates with an upwardly open recess 54. Recess 54 is influid communication with discharge fitting 24 defined by cap 16 andpartition 56, such that compressed fluid exits the shell 14 via passage52, recess 54, and fitting 24. Non-orbiting scroll member 48 is designedto be mounted to bearing housing 46 in a suitable manner such asdisclosed in the aforementioned U.S. Pat. No. 4,877,382 or U.S. Pat. No.5,102,316, the disclosures of which are incorporated herein byreference.

Referring now to FIGS. 2 and 3, electrical enclosure 28 includes a lowerhousing 58, an upper housing 60, and a cavity 62. The lower housing 58is mounted to the shell 14 using a plurality of studs 64 which arewelded or otherwise fixedly attached to the shell 14. The upper housing60 is matingly received by the lower housing 58 and defines the cavity62 therebetween. The cavity 62 may be operable to house respectivecomponents of the compressor protection and control system 12.

With particular reference to FIG. 4, the compressor 10 is shown as atwo-step compressor having an actuating assembly 51 that selectivelyseparates the orbiting scroll member 40 from the non-orbiting scrollmember 48 to modulate the capacity of the compressor 10. The actuatingassembly 51 may include a solenoid 53 connected to the orbiting scrollmember 40 and a controller 55 coupled to the solenoid 53 for controllingmovement of the solenoid 53 between an extended position and a retractedposition.

Movement of the solenoid 53 in the extended position separates the wraps42 of the orbiting scroll member 40 from the wraps 50 of thenon-orbiting scroll member 48 to reduce an output of the compressor 10.Conversely, retraction of the solenoid 53, moves the wraps 42 of theorbiting scroll member 40 closer to the wraps 50 of the non-orbitingscroll member 48 to increase an output of the compressor 10. In thismanner, the capacity of the compressor 10 may be modulated in accordancewith demand or in response to a fault condition. The actuation assembly51 is preferably of the type disclosed in assignee's commonly-owned U.S.Pat. No. 6,412,293, the disclosure of which is incorporated herein byreference.

With reference to FIGS. 2-11, the protection and control system 12generally includes a pair of sensors 66, 68, processing circuitry 70,and a power interruption system 72. The sensors 66, 68 of protection andcontrol system 12 detect cumulating parameters of the system 11 todiagnose operating conditions and faults under both normal and abnormalfault conditions. The parameters detected by sensors 66, 68 are referredto as cumulating sensors because the processing circuitry 70 diagnosesconditions of the compressor 12 and system 11 by analyzing trends andrelationships among data detected by one or both of sensors 66, 68. Inaddition, the processing circuitry 70 may be in communication withcontroller 55 to control compressor modulation based on systemconditions detected by sensors 66, 68 or faults determined by theprocessing circuitry 70.

Sensor 66 generally provides diagnostics related to high-side faultssuch as compressor mechanical failures, motor failures, and electricalcomponent failures such as missing phase, reverse phase, motor windingcurrent imbalance, open circuit, low voltage, locked rotor currents,excessive motor winding temperature, welded or open contactors, andshort cycling. Sensor 66 monitors compressor current and voltage todetermine, and differentiate between, mechanical failures, motorfailures, and electrical component failures and may be mounted withinelectrical box 28, as shown in FIG. 2, or may be incorporated inside theshell 14 of the compressor 10, as shown in FIG. 3. In either case,sensor 66 monitors current draw by the compressor 10 and generates asignal indicative thereof, such as disclosed in assignee'scommonly-owned U.S. Pat. No. 6,615,594 and U.S. patent application Ser.No. 11/027,757, filed on Dec. 30, 2004, which claims benefit of U.S.Provisional Patent Application No. 60/533,236, filed on Dec. 30, 2003,the disclosures of which are incorporated herein by reference.

While sensor 66 as described herein may provide compressor currentinformation, the control system 12 may also include a discharge pressuresensor 13 mounted in a discharge pressure zone or a temperature sensor15 mounted in an external system such as a condenser (FIG. 16). Any orall of the foregoing sensors may be used in conjunction with sensor 66to provide the control system 12 with additional system information.

Sensor 66 provides the protection and control system 12 with the abilityto quickly detect high-side faults such as a system fan failure orrefrigerant overcharging without requiring independent sensors disposedthroughout the compressor 10 and system 11. For example, because currentdrawn by the compressor 10 increases quickly with high-side pressure ata given voltage, a pressure increase at the high-side of the compressor10 is quickly detected and reported to the processing circuitry 70 asthe compressor 10 draws additional current. For example, when aninternal compressor component experiences a fault, such as alocked-rotor condition, the compressor motor 32 draws additional currentin an effort to free the locked condition. When the motor 32 drawsadditional current, sensor 66 detects the increase in current draw andsignals the processing circuitry 70.

In general, sensor 66 measures current drawn by the motor 32 andindicates system high-side faults such as overcharged refrigerant, dirtyheat-exchanger coils, or condenser-fan failure within the system 11.Each of the aforementioned faults causes the compressor 10 to increasethe pressure of the refrigerant to force the refrigerant throughout thesystem 10. For example, when a heat-exchanger coil is blocked, acondenser fan is seized, or the refrigerant is overcharged, therefrigerant within the system 11 does not fully vaporize and thecompressor 10 is forced to push liquid-phase refrigerant through thesystem 11.

The compressor 10 works harder to move liquid refrigerant through thesystem 11 versus moving a vaporized refrigerant through the same system11 because liquid refrigerant experiences a greater frictionalresistance (i.e., between the refrigerant and conduit(s) of the system11). Furthermore, liquid refrigerant is more dense than vaporizedrefrigerant and therefore requires greater condenser pressure than wouldan equivalent amount of vaporized refrigerant. When the compressor 10 isforced to work harder, the motor 32 draws additional current, which isdetected by sensor 66 and reported to the processing circuitry 70.

Sensor 68 generally provides diagnostics related to low-side faults suchas a low charge in the refrigerant, a plugged orifice, a evaporatorblower failure, or a leak in the compressor. Sensor 68 may be disposedproximate to the discharge outlet 24 or the discharge passage 52 (FIG.4) of the compressor 10 and monitors a discharge line temperature of acompressed fluid exiting the compressor 10. The sensor 68 may be locatedproximate to the compressor outlet fitting 24, generally external to thecompressor shell 14, as shown in FIG. 2. Locating sensor 68 external ofthe shell 14, allows flexibility in compressor and system design byproviding sensor 68 with the ability to be readily adapted for use withpractically any compressor and in any system.

While sensor 68 may provide discharge line temperature information, thecontrol system 12 may also include a suction pressure sensor 17 orlow-side temperature sensor 19 (i.e., either mounted proximate an inletof the compressor 10 or mounted in an external system such as anevaporator). Any, or all of the foregoing sensors may be used inconjunction with sensor 68 to provide the control system 12 withadditional system information.

While sensor 68 may be positioned external to the shell 14 of thecompressor 10, the discharge temperature of the compressor 10 maysimilarly be measured within the shell 14 of the compressor 10, as shownin FIG. 3. A discharge port temperature, taken generally at thedischarge fitting 24, could be used in place of the discharge linetemperature arrangement shown in FIG. 2. A hermetic terminal assembly 74may be used with such an internal discharge temperature sensor tomaintain the sealed nature of the compressor shell 14, and, can easilybe accommodated by a hermetic terminal assembly.

Sensor 68 provides the protection and control system 12 with the abilityto quickly detect low-side faults such as a blower failure or a loss ofrefrigerant charge without requiring independent pressure andsuction-temperature sensors disposed throughout the compressor 10 andsystem 11. The sensor 68 detects and monitors discharge linetemperature, and, as such, is a strong cumulating point of compressionheat. Thus, sensor 68 is able to quickly detect a rise in temperaturewithin the compressor 10 and send a signal to the processing circuitry70.

Common causes of an increased discharge line temperature include a lossof refrigerant charge of a restricted flow of refrigerant due to blowerfailure or blocked orifice because the amount of refrigerant enteringthe low-side, or suction side, of the compressor 10 is reduced. When theflow of refrigerant is decreased, the power consumed by the compressormotor 32 and associated internal components exceeds the amount needed tocompress the entering refrigerant, thereby causing the motor 32 andassociated internal components of the compressor 10 to experience a risein temperature. The increased motor and component temperature ispartially dissipated to the compressed refrigerant, which is thensuperheated more than under normal operating conditions. Sensor 68detects the increase in compressed refrigerant temperature as therefrigerant exits the shell 14 through discharge fitting 24.

The relationship between discharge superheat and suction superheat isprovided in FIG. 5. In general, the relationship between dischargesuperheat and suction superheat is generally linear under most low-sidefault conditions and governed by the following equation where SH_(d) isdischarge superheat, SH_(s) is suction superheat, and T_(Amb) is ambienttemperature:SH _(d)=(1.3*SH _(s)+30 degrees F.)+(0.5*(T _(Amb)−95 degrees F.))

The generally linear relationship between suction superheat anddischarge superheat allows sensor 68 to quickly detect an increase insuction superheat, even though sensor 68 is disposed near an outlet ofthe compressor 10. The relationship between discharge temperature andsuction temperature is further illustrated in FIG. 6, which shows howdischarge line temperature is affected by an increase in suction linetemperature. The relationship shown in FIG. 6 allows sensor 68 toquickly detect a low side fault caused by a high suction temperature(such as a low charge condition or a plugged orifice), even thoughsensor 68 is disposed near an outlet of the compressor 10.

In addition to determining low-side faults associated with a rise insuction temperature, sensor 68 is also able to detect faults associatedwith changes in suction pressure. FIG. 7 shows how suction pressuredecreases rapidly for a low-side fault, such as loss of charge orcompressor high-low leak. The rapid decrease in suction pressure causesa concurrent increase in suction, thus causing an increase in dischargeline temperature, as shown in FIG. 6. Therefore, the control system 12is able to declare a low-side fault (such as a restricted thermalexpansion valve) based on readings from sensor 68, as will be describedfurther below with respect to FIGS. 12 and 13.

When the compressor 10 is initially started after a sufficiently longoff period, the initial discharge line temperature is generally closeto-ambient temperature as the compressor 10 has yet to cycle refrigerantthrough the system. To account for different environments (i.e.,different ambient conditions), and to reduce the influence of theenvironment on the ability of sensor 68 to quickly and accuratelymonitor the discharge line temperature, sensor 68 monitors the rise indischarge line temperature within the first thirty to sixty secondsfollowing startup of the compressor 10.

The sensor eliminates the necessity of the compressor 10 to reach asteady state prior to taking a temperature reading. For example, suctionpressure decreases the fastest during the first thirty to sixty secondsof compressor operation under low-side fault conditions. The decrease insuction pressure results in a higher compression ratio and moreoverheating. The overheating is detected by sensor 68 within the firstthirty to sixty seconds of compressor operation. Without such anarrangement, sensor 68 may become sensitive to the surroundingenvironment, thereby increasing the time in which sensor 68 must wait totake a temperature reading. By taking the temperature reading shortlyafter startup (i.e., within thirty to sixty seconds), sensor 68 is ableto quickly and consistently detect a low-side fault such as loss ofsuction pressure, independent of ambient conditions.

Generally speaking, a high-side or a low-side sensor value changes withthree basic operating stages of the compressor 10; start-up,quasi-steady state, and steady-state. The values taken at each stage maybe used by the control system 12 to monitor and diagnose high-side andlow-side faults. For example, FIG. 8 shows a plot of a high-side orlow-side sensor during start-up, quasi-steady state, and steady-statestages of an exemplary compressor 10. For a normal plot, discharge linetemperature and current should typically increase gradually during thefirst sixty seconds of start-up and should start to become more linearduring the quasi-steady state stage, which could take approximately 10minutes. Once in the steady-state stage, the plot should be constant(i.e., no changes in readings taken by sensors 66, 68) and should remainas such throughout operation of the compressor 10 unless ambienttemperature changes suddenly. By monitoring the rate of change ofsensors 66, 68 over time, each time period (i.e., start-up, quasi-steadystate, and steady state) can be determined for various operating ambienttemperatures.

For example, a defrost cycle can be detected for a heat pump operatingin a heating mode when the sensors 66, 68 detect a sudden change incurrent and/or discharge line temperature. The change in current anddischarge line temperature is a result of the compressor 10 ceasingoperation to allow the system 11 to perform a defrost. Therefore,sensors 66, 68, in combination with processing circuitry 70, are able todetect a defrost cycle during compressor start-up, quasi-steady state,and steady-state operating conditions.

If a defrost cycle is not realized for a predetermined amount of time(i.e., generally more than six hours of compressor run time) than thecontrol system 12 can declare a stuck reversing valve. When thesteady-state is not realized, such that sensors 66, 68 do not reach astabilized state, the control 12 system may declare that a thermalexpansion valve is “hunting.” The thermal expansion valve is deemed tobe “hunting” when the valve continuously modulates its position (i.e.,“hunting” for a steady-state position).

For a low-side fault, discharge line temperature increases more rapidlyduring start-up as compared to the normal plot. As such, higher sensorvalues are realized during the quasi-steady state and steady-statestages. Therefore, the control system 12 is able to quickly determine alow-side fault based on the sharp rise in discharge line temperatureduring start-up and then is further able to confirm the fault whenhigher-than-normal conditions are also realized during both thequasi-steady state and steady-state stage.

Sensor 68 monitors the discharge line temperature of the compressor 10during periods where the responses in suction and/or discharge pressuresare most representative of the system fault. In other words, dependingon the correlation between the sensed temperature and the time in whichthe temperature is taken, indicates a particular fault. Discharge linetemperature typically increases with compression ratio and suctionsuperheat. Therefore, several specific low-side system faults can bedifferentiated such as restricted flow orifice, system fan failure(i.e., an evaporator or condenser fan, etc.), loss of refrigerantcharge, or compressor internal leak by analyzing the different dischargeline temperature signatures. FIG. 12 shows an example of a low-sidesensor response as represented by the compressor discharge linetemperature under normal condition versus a low-refrigerant chargecondition. It can be seen that the rise in discharge line temperature issignificantly different in the first thirty to sixty seconds as well asduring the steady-state condition between the normal and low-side faultmodes. FIG. 13 shows further an illustration of how all other faultmodes could be detected differentially by sensor 68 within the firstthirty to sixty second period versus the longer time periods aftercompressor start up.

The thirty to sixty second time period can be adjusted as needed toaccommodate differences between cooling and heating modes of a heat pumpthrough use of an ambient temperature sensor (described below). Itshould be noted that it is also possible to set this time perioddifferently for various capacity stages in the case of avariable-capacity compressor. By comparing the signals produced bysensor 66 with those with sensor 68, low-side and high-side faults canbe accurately and quickly differentiated by the processing circuitry 70,as will be discussed further below.

The high-side and low-side signals produced by sensors 66, 68,respectively, are sent to the processing circuitry 70 to compare theoperating parameters to base-line parameters, as shown in FIGS. 10 and11. The base-line parameters are determined at installation of thecompressor 10 to determine “normal” or no-fault operating conditions forthe compressor 10 and system 11.

At installation, the “signature” of compressor current versus time isdetermined for use in differentiating high-side faults such as condenserfan failure versus refrigerant overcharging. The “signature” of thecompressor current versus time is referred to as the baseline reading(BL) for the system and is used in determining fault conditions. Thecalibration of sensor 66 for a particular compressor size orinstallation can be avoided by adaptively detecting the normal, no-faultcurrent versus ambient temperatures during the first 24 to 48 hours ofoperation following initial installation.

The no-fault signature of current versus time provides the processingcircuitry 70 with a baseline to use in comparing current sensed bysensors 66, 68. For example, the processing circuitry 70 will declare ahigh-side fault when the sensed current exceeds this initial baselinevalue by a predetermined amount, as shown in FIG. 14. It should be notedthat in addition to sensor 66, that voltage sensing might further berequired to allow for adjustment for current due to voltage fluctuationin the field.

An ambient temperature sensor 76 is provided for use in calculating thecompressor current versus time, whereby the ambient temperature sensor76 provides the ambient temperature for the given environment. For lowercost, the ambient sensor 76 can also be incorporated directly onto anelectronic circuitry board of the controller that provides theprocessing circuitry 70. Alternatively, the ambient temperature for agiven environment can be determined by performing a regression equationfitting the discharge line temperature, the sensed ambient temperaturereading, and the compressor-off time. Also, the initial discharge linetemperature value determined at compressor start-up can be used as anapproximation of ambient temperature as ambient temperature does notusually change over the first ten to 15 minutes of compressor operation.

With particular reference to FIGS. 9-17, operation of the protection andcontrol system 12 will be described in detail. Generally speaking, thecompressor protection and control system 12 uses the compressor 10 as asystem sensor with two cumulating parameters. Because a high-side faulttypically causes a faster response than a low-side fault, the priorityis to first use compressor current to determine if a high-side faultexists before proceeding to determine any low-side faults. In thismanner, the compressor protection and control system 12 is able toquickly sense and differentiate between high-side and low-side faults.

FIG. 16 shows the compressor 10 incorporated into a heat pump system 11having an evaporator coil 80, a condenser 82, an evaporator fan 84, acondenser fan 86, and an expansion device 88. The protection and controlsystem 12 is incorporated into the system 11 to detect and differentiatebetween high-side faults such as system fan failure or refrigerantovercharging and low-side faults such as evaporator or condenser fanfailure and low-refrigerant charge.

At installation, the baseline signature of compressor current versustime is determined for use in differentiating high-side faults. Once thebaseline is determined, the processing circuitry 70, in combination withsensors 66, 68, serves to monitor and diagnose particular compressor andsystem faults. The processing circuitry 70 works in conjunction withsensors 66, 68 to direct the power interruption system 72 to toggle thecompressor between a normal operating mode, a reduced-capacity mode, anda shutdown mode.

Control algorithms for sensors 66, 68 are provided at FIGS. 10 and 11.It should be noted that the data ranges defining individual high-sideand low-side faults in FIGS. 10 and 11 are exemplary in nature, and assuch, may be modified for different systems.

At startup of the compressor 10, sensor 66 measures the relative current(i.e., as compared to the baseline) to determine if a high-side faultexists. The processing circuitry 70 receives current and voltage datafrom sensor 66 and processes the data into a power-consumption-over-timesignature. Specifically, the processing circuitry 70 receives thecurrent and voltage data and determines the power (VA) by the followingformula: VA=current*voltage. The power value (VA) is then compared tothe baseline signature (BL) determined at installation undernormal/no-fault operating conditions.

If the power drawn by the motor 32 is greater than about 1.3 times thebaseline signature (current over time) for the first 30 seconds ofoperation, the processing circuitry 70 determines a high-side fault. Theprocessing circuitry 70 determines a high-side fault (either that therefrigerant is overcharged or that the condenser coil is dirty) based onthe value of the measured current being relatively higher than nominal(i.e., about 1.3 times the baseline signature), as shown in FIG. 10 and14. In contrast, the processing circuitry 70 determines a low-side fault(either low refrigerant or evaporator coil is dirty) based on themeasured current being relatively lower than nominal (i.e., about 0.9times the baseline signature).

If the detected value is about 1.5 times greater than the baselinesignature within 30 seconds of operation and the current drawn by themotor 32 after the first ten minutes is less than about 0.7 times thebase line value, the processing circuitry 70 indicates a differenthigh-side failure mode. Specifically, if the current drawn by the motor32 is greater than about 1.5 times the baseline value for the first 30seconds and the current drawn by the motor 32 after the first tenminutes is less than about 0.7 times the base line value, then theprocessing circuitry 70 indicates a condenser-fan failure, as best shownin FIG. 14. This significant change is detected as a condition due tocompressor motor stalling and reversing direction. In either event, theprocessing circuitry 70 will direct the power interruption system 72 torestrict power to the compressor 10 to either stop operation or to allowthe compressor 10 to function in a reduced capacity.

Sensor 68 works with sensor 66 to provide the processing circuitry 70with enough information to quickly and accurately determine thecompressor and system operating parameters within 30 seconds of startup.Within the first 30 seconds of startup, sensor 68 measures dischargeline temperature and creates a signal indicative thereof. The signal issent to the processing circuitry 70 to determine the proper operatingmode for the compressor (i.e., normal mode, reduced-capacity mode, orshutdown mode), as shown in FIG. 15.

If the sensed temperature rise after compressor start up is greater than70 degrees for example (roughly 1.5 times normal), and the powerconsumption is less than about 0.9 times the baseline value after tenminutes, a low charge or plugged orifice fault is declared, as bestshown in FIG. 13. If the sensed temperature rise is less than 50 degreeswithin the first 30 seconds of operation, but greater than 100 degreesafter 15 minutes of operation, with a power value of less than about 0.9times the baseline after ten minutes of operation, a blower failure orthermal expansion valve failure is declared, as best shown in FIG. 13.If the sensed temperature is less than 45 degrees after the first 30seconds of operation, but greater than 25 degrees after the first 15minutes of operation, with a power value of less than about 0.9 timesthe baseline after ten minutes of operation, a blower failure or pluggedorifice fault is declared. Finally, if the sensed temperature is lessthan 25 degrees, with a power value of less than about 0.9 times thebaseline after ten minutes of operation, a compressor leak is declared.

If the processing circuitry 70 determines that the compressor 10 andsystem 11 are functioning within predetermined operating parameters, thesystem 70 will allow operation of the compressor 10 and system 11. Theprocessing circuitry 70 works in conjunction with sensors 66, 68 todifferentiae between a high-side and a low-side compressor and systemfaults. Additionally, the processing circuitry 70 and sensors 66, 68function to differentiate between specific high-side and low-side faultsto direct a homeowner or serviceperson to the particular compressor orsystem fault. In doing so, the priority is to first use compressorcurrent to determine if there is a high-side fault before proceeding todetermine any low-side faults. In this manner, the two faults (i.e.,high-side and low-side) can be differentiated over time in terms ofwhich occurred first to quickly and accurately determine a specific highor low-side fault.

The protection and control system 12 further includes a plurality oflight emitting devices (LEDs) to alert a user as to the state of thecompressor and system 10, 12. In one configuration, the system 12includes a green LED, a yellow LED, and a red LED 90, 92, 94, as shownin FIGS. 1 and 9. The green LED 92 is illuminated when the compressor isfunctioning under normal conditions and no fault is detected by sensors66, 68. The yellow LED 94 is illuminated to designate a system fault.Specifically, if the sensors 66, 68 detect a fault condition using thecontrol algorithms previously discussed, the processing circuitry 70will illuminate the yellow LED 92 to alert a user of a system fault. Itshould be noted that the when a system fault is detected, but thecompressor 10 is otherwise functioning normally, that the yellow LED 92will be illuminated to denote that the compressor 10 is functioningwithin predetermined acceptable parameters, but that the system 11 isexperiencing a system-related fault.

The red LED 94 is only illuminated when the compressor 10 experiences aninternal compressor fault. In this manner, when both the compressor 10and system 11 experience a fault, both the green and red LEDs 90, 94will be illuminated. When a compressor fault is detected, only the redLED 94 will be illuminated. In sum, the green, yellow, and red LEDs 90,92, 94 are independently illuminated to specifically differentiatebetween compressor and system faults. Such a distinction proves to be avaluable tool to the user or repairperson. For example, a user orrepairperson can quickly look to the LEDs 90, 92, 94, displayed on theelectrical box 28 of the compressor 10, and quickly diagnose theproblem. As can be appreciated, such a diagnostic system preventsincorrect diagnosis and unnecessary replacement of functioningcompressors.

The processing circuitry 70 may communicate the compressor and systemfault status and data to a central system in addition to illuminatingthe LEDs 90, 92, 94. In other words, the processing circuitry 70 may belinked to a network 100 to provide compressor and system operatingparameters (FIG. 17). Compressor and system operating parameters may becollected and analyzed by the network 100 to anticipate and protectagainst future compressor and/or system faults. For example, if a thecompressor 10 experiences a broken seal at or around a certain number ofcycles, an operator can plan to service the compressor 10 during ashutdown period, rather than shut down the compressor 10 and system 11during normal use. As can be appreciated, such scheduled maintenanceprevents shutting down the compressor 10 and system 11 during normaluse, thereby increasing compressor and system efficiency.

The system controller can confirm the diagnosis of the processingcircuitry 70 by independently checking the status of other sensors andcomponents that it may have access to, such as fan speed, coiltemperature, etc. For example, the system controller can confirm a fanfailure finding of the processing circuitry 70 based on fan speed dataavailable to the controller.

The network 100, in addition to including a system controller, can alsoinclude a hand-held computing device such as a personal data assistantor a smart cell phone, schematically represented as 71 in FIG. 17. Thehand-held computing device 71 can be used by a technician orrepairperson to communicate with the processing circuitry 70. Forexample, the hand-held device provides the technician or repairpersonwith the ability to instantly check compressor operating conditions(i.e., discharge line temperature and current data, for example) eitherlocally (i.e., on-site) or from a remote location. As can beappreciated, such a device becomes useful when a plurality ofcompressors 10 are linked to a system controller over a large network100 as compressor operating data can be quickly requested and receivedat any location within a facility.

As previously discussed, the processing circuitry 70 receives high-sideand low-side signals from respective sensors 66, 68 to dictate thecompressor mode via the power interruption system 72. The combination ofthe current sensing (i.e., sensor 66) and the discharge line temperature(i.e., sensor 68) provides an opportunity for performing “smart” systemprotection.

The smart system provides the protection and control system 12 with theability to differentiate between “soft” and “hard” protection. Forexample, upon detection of a low-side fault, “soft” mode would allowcontinued operation of the compressor with intermittent powerrestriction in an effort to allow the compressor 10 to operate in areduced fashion, as shown in FIG. 15. The reduced operation of thecompressor 10 is allowed to provide continued refrigeration (or heatingin a heat pump application) prior to repair provided that the reducedoperation is deemed safe. Such operation of the compressor 10 may beachieved through use of actuation assembly 51.

For example, if a particular low-side fault permits operation of thecompressor 10 at a reduced capacity (i.e., a so-called “limp-alongmode”), the actuation assembly 51, through controller 55, may separateorbiting scroll wraps 42 from non-orbiting scroll wraps 50 throughinteraction between the solenoid 53 and the orbiting scroll member 40.Separation of orbiting scroll wrap 42 from non-orbiting scroll wrap 50permits a reduction in compressor capacity and therefore allows thecompressor 10 to operate during certain low-side faults.

However, if a severe high-temperature low-side fault (i.e., dischargeline temperature above 260 degrees F.) is detected, or a severe lowtemperature low-side fault (i.e., discharge line temperature below 135degrees F.), the processing circuitry 70 will direct the powerinterruption system 72 to place the compressor 10 into the shutdown modeuntil repairs are performed, as shown in FIG. 15.

While FIG. 15 depicts an operating temperature range for low-sidefaults, it should be understood that temperature ranges definingcompressor operating modes for low-side faults may range depending onthe particular compressor 10 or system 11. In other words, the specificranges defining normal, reduced-capacity, and shutdown modes may varydepending on the particular compressor 10 and application. A similargraph could be created for defining a normal, reduced-capacity, andshutdown mode using specific high-side faults. Such an arrangement woulddefine acceptable power consumption ranges for the compressor and wouldtherefore dictate acceptable faults under which the compressor 10 couldcontinue operation under a reduced-capacity mode without causing damage.Again, high-side ranges defining acceptable operating parameters maysimilarly fluctuate depending on the particular compressor 10 and system11.

The processing circuitry 70 is able to dictate the specific operatingmode for the compressor 10 by knowing the cause of a particularhigh-side or low-side fault. For example, if the circuitry 70 knows thata particular low-side fault will trip an internal protector 102 in 45minutes, the compressor 10 may continue to run safely for about 30minutes. Such a fault places the compressor 10 in the “soft” mode,whereby the processing circuitry 70 directs the power interruptionsystem 72 to restrict power to the compressor 10 at 30 minutes to avoidtripping the internal protector 102 and/or separates the orbiting scrollwrap 42 from the non-orbiting scroll wrap 48 via actuation assembly 51.

A “hard” mode disrupts power to the compressor 10 to effectivelyshutdown further operation until service and repairs are performed. The“hard” mode is only engaged if necessary to protect the compressor andsystem 10, 11 and to prevent major repairs. Again, the only way for theprocessing circuitry 70 to know if continued operation is acceptable isto know the particular cause of the fault. In the case of the “hard”mode, the processing circuitry 72 directs the power interruption system72 to restrict all power to the compressor 10, thereby placing thecompressor 10 in the shutdown mode.

In addition to sensing and diagnosing high-side and low-side faults, thecompressor protection and control system 12 also provides the user withthe ability to track and control power consumption and energy usage bythe compressor 10. FIG. 17 shows a schematic diagram incorporating apower consumption algorithm into the network 100. Monitoring and storingcurrent and voltage data, allows the user to estimate compressor powerconsumption. Specifically, by multiplying the voltage by the current,power consumption for the compressor and system 10, 11 can bedetermined.

By multiplying the product of voltage and current by an estimated powerfactor, power consumption for the compressor 10 and system 11 can beaccurately determined. The power factor essentially corrects thesupplied power reading from a utility meter and provides an indicationof the actual power consumed (i.e., actual power consumed by thecompressor 10). The power data can be integrated over time to provideenergy usage data such as kilowatts per day/month. Such data may beuseful for energy and system performance analysis.

As described, the compressor protection and control system 12 receivesdischarge line temperature data from sensor 68 and current data fromsensor 66 to determine, and differentiate between, high-side andlow-side faults. The information is used generally to determine, anddifferentiate between, high-side and low-side faults to better diagnosecompressor and system failures. In addition to the foregoing, suchinformation can also be used to determine other operating parametersassociated with the compressor 10 and system 11. Specifically, dischargeline temperature data and current data can be used to determinecondenser temperature, evaporator temperature, suction superheat,discharge superheat, compressor capacity, and compressor efficiency.Such information is useful in optimizing compressor and system operationas well as in simplifying and streamlining compressor installation, aswill be described further below.

With reference to FIG. 18, a fault tree 110 is provided that illustrateshow the compressor protection and control system 12 uses the dischargeline temperature and current information to determine specific faultsrelated to compressor operation, using such variables as condensertemperature and evaporator temperature. The evaporator and condensertemperatures are determined from the discharge line temperature andcurrent data obtained by sensors 66, 68, as will be described furtherbelow.

When the system 11 experiences an insufficient cooling or no coolingcondition, the system 12 determines if the compressor 10 has failed, isrunning but cycles on a protector, or is running but at low capacity. Ifthe compressor 10 has failed, the control system 12 differentiatesbetween an electrical failure and a mechanical failure. If the failureis deemed an electrical failure, the system 12 checks the compressormotor and associated electrical components. If the failure is deemed amechanical failure, the system 12 checks for a locked rotor condition.

If the compressor 10 is running but cycles on a protector, the system 12determines if the system is experiencing a low voltage condition. Inaddition, the system 12 also checks for a high condensertemperature/high current condition or for a low evaporatortemperature/low current condition. If a high condenser temperature/highcurrent condition is determined, a high-side fault is declared. If a lowevaporator temperature/low current condition is determined, a low-sidefault is declared. If a low evaporator temperature/low current conditionis determined in conjunction with a high discharge temperature, thesystem 12 is further able to declare that the fault is either a loss ofcharge, a plugged orifice, or a blower/thermal expansion valve failure.If a low evaporator temperature/low current condition is determined inconjunction with a low discharge temperature, the system 12 is furtherable to declare that the fault is either a blower/orifice failure or anoversized orifice.

If the compressor 10 is running, but at low capacity, the system 12checks for a high evaporator/low current condition. If the highevaporator/low current condition is accompanied by a low dischargetemperature, the system 12 declares an internal compressor hi-low leak.

The above fault tree 110 relies on evaporator temperature and condensertemperature readings in addition to the current and dischargetemperature readings to determine the fault experienced by thecompressor 10 or system 11. The system 12 can obtain such information byuse of temperature or pressure sensors disposed in each of theevaporator 80 or the condenser 82. In such a system, the temperature orpressure readings are simply read by the individual sensor and deliveredto the processing circuitry 70 for processing or could be obtained fromanother system controller. Alternatively, use of such sensors, whileeffective, increases the cost and complexity of the overall system cost.

As a preferred alternative to use of such sensors, the present system 12can alternatively determine the evaporator temperature and condensertemperature based solely on the discharge line temperature and currentinformation received from sensors 66, 68. With reference to FIG. 19, agraph showing compressor power as a function of evaporator temperature(T_(evap)) and condenser temperature (T_(cond)). As shown, power remainsfairly constant irrespective of evaporator temperature. Therefore, whilean exact evaporator temperature is determined by a second degreepolynomial (i.e., a quadratic function), for purposes of control, theevaporator temperature can be determined by a fist degree polynomial(i.e., linear function) and can be approximated as roughly 45 degreesF., for example in a cooling mode. In other words, the error associatedwith choosing an incorrect evaporator temperature is minimal whendetermining condenser temperature.

The graph of FIG. 19 includes compressor power on the Y-axis andcondenser temperature on the X-axis. Compressor power P is determinedthrough application of the following equation, where A is the measuredcompressor current obtained by sensor 66 and V is the measured voltage V(Obtained by a voltage sensor):P=V*A

The condenser temperature is calculated for the individual compressorand is therefore compressor model and size specific. The followingequation is used in determining condenser temperature, where P iscompressor power, C0-C9 are compressor-specific constants, T_(cond) iscondenser temperature, and T_(evap) is evaporator temperature:P=C 0+(C 1*T _(cond))+(C 2*T _(evap))+(C 3*T _(cond){circumflex over( )}2)+(C 4*T _(cond) *T _(evap))+(C 5*T _(evap){circumflex over( )}2)+(C 6*T _(cond){circumflex over ( )}3)+(C 7*T _(evap) *T_(cond){circumflex over ( )}2)+(C 8*T _(cond) *T _(evap){circumflex over( )}2)+(C 9*T _(evap){circumflex over ( )}3)

The above equation is applicable to all compressors, with constantsC0-C-9 being compressor model and size specific, as published bycompressor manufacturers, and can be simplified as necessary by reducingthe equation to a second-order polynomial with minimal compromise onaccuracy. The equations and constants can be loaded into the processingcircuitry 70 by the manufacturer, in the field during installation usinga hand-held service tool, or downloaded directly to the processingcircuitry 70 from the internet.

The condenser temperature, at a specific compressor power (based onmeasured current draw by sensor 66), is determined by referencing a plotof evaporator temperature (as either a first degree or a second degreepolynomial) for a given system versus compressor power consumption. Thecondenser temperature can be read by cross-referencing a measuredcurrent reading against the evaporator temperature plot. Therefore, thecondenser temperature is simply a function of reading a current drawn atsensor 66. For example, FIG. 13 shows an exemplary power consumption of3400 watts (as determined by the current draw read by sensor 66). Theprocessing circuitry 70 is able to determine the condenser temperatureby simply cross-referencing power consumption of 3400 watts for a givenevaporator temperature (i.e., 45 degrees F., 50 degrees F., 55 degreesF., as shown) to determine the corresponding condenser temperature. Itshould be noted that the evaporator temperature can be approximated asbeing either 45 degrees F., 50 degrees F., or 55 degrees F. withoutmaterially affecting the condenser temperature calculation. Therefore,45 degrees F. is typically chosen by the system 12 when making the abovecalculation.

With reference to FIG. 20, once the condenser temperature is known, theexact evaporator temperature can be determined by plotting dischargeline temperature versus condenser temperature. It should be noted thatthe evaporator temperature used in determining the condenser temperatureis an approximated value (typically between 45-55 degrees F.). Theapproximation does not greatly affect the condenser temperaturecalculation, and therefore, such approximations are acceptable. However,when making capacity and efficiency calculations, the exact evaporatortemperature is required.

The evaporator temperature is determined by referencing a discharge linetemperature, as sensed by sensor 66, against the calculated condensertemperature (i.e., from FIG. 19) and can be accurately determinedthrough iterations. The resulting evaporator temperature is a morespecific representation of the true evaporator temperature and istherefore more useful in making capacity and efficiency calculations.

Once the condenser and evaporator temperatures are known, the compressormass flow, compressor capacity, and compressor efficiency can all bedetermined. Compressor mass flow is determined by plotting condensertemperature and evaporator temperature as a function of mass flow(bm/hr) and discharge line temperature. The mass flow is determined byreferencing the intersection of evaporator temperature and condensertemperature at a sensed discharge line temperature. For example, FIG. 21shows that for a 180 degrees F. discharge line temperature, a 120degrees F. evaporator temperature, and a 49 degrees F. evaporatortemperature, the mass flow of the compressor is roughly 600 bm/hr.

FIG. 22 is a flowchart that demonstrates both a compressor capacityalgorithm and a compressor efficiency algorithm. Both algorithms usedischarge line temperature and current in making the capacity andefficiency calculations.

Compressor capacity is determined by first obtaining discharge linetemperature and current data from respective sensors 66, 68. Once thedata is collected, the compressor nominal capacity size is referenced bythe processing circuitry 70 to establish constants C0-C9. The above dataallows the processing circuitry 70 to calculate condenser temperatureand evaporator temperature, as previously discussed. Such informationfurther allows the processing circuitry 70 to determine compressorcapacity information through application of the following equation,where X is compressor capacity, Y0-Y9 are compressor-specific constants,T_(cond) is condenser temperature, and T_(evap) is evaporatortemperature:X=Y 0+(Y 1*T _(cond))+(Y 2*T _(evap))+(Y 3*T _(cond){circumflex over( )}2)+(Y 4*T _(cond) *T _(evap))+(Y 5*T _(evap){circumflex over( )}2)+(Y 6*T _(cond){circumflex over ( )}3)+(Y 7*T _(evap) *T_(cond){circumflex over ( )}2)+(Y 8*T _(cond) *T _(evap){circumflex over( )}2)+(Y 9*T _(evap){circumflex over ( )}3)

The above equation is applicable to all compressors, with constantsY0-Y-9 being compressor model and size specific, as published bycompressor manufacturers. The equations and constants can be loaded intothe processing circuitry 70 by the manufacturer or in the field duringinstallation using a hand-held service tool. The equations and constantscan be loaded into the processing circuitry 70 by the manufacturer, inthe field during installation using a hand-held service tool, ordownloaded directly to the processing circuitry 70 from the internet.

With reference to FIG. 23, compressor capacity can be determined fordifferent evaporator temperatures by plotting compressor capacity versuscondenser temperature. Compressor nominal tonnage size can be determinedby plotting compressor power versus ambient temperature, as shown inFIG. 24. In this manner, for a given compressor with predefinedconstants (i.e., Y0-Y9), the processing circuitry simply references thecalculated condenser temperature against the calculated evaporatortemperature or compressor tonnage to determine the compressor capacity.

Compressor efficiency is determined by plotting the evaporatortemperature as a function of compressor efficiency and condensertemperature. Condenser and evaporator temperatures are determined bymeasuring discharge line temperature and current at sensors 66, 68. Oncethe processing circuitry 70 determines the evaporator temperature andcondenser temperature, the compressor efficiency can be determined, asshown in FIG. 25.

System efficiency is determined by first determining the net evaporatorcoil capacity by adjusting for suction line superheat and blower heat,as shown in FIG. 22. The suction line superheat is determined by firstdetermining discharge superheat using the following equation:SH _(d)=Discharge Line Temperature−T _(cond)

Once the discharge superheat is determined, the suction superheat can bedetermined using the following equation, graphically represented in FIG.5:SH _(d)=(1.3*SH _(s)+30°)+(0.5*(T _(Amb)−95°))

The system efficiency is derived as a ratio of the net evaporator coilcapacity over the sum of compressor, fan, and blower power once thesystem is at steady-state. Determining system efficacy at eitherstart-up or quasi-steady state does not provide a reliable indication ofsystem efficiency. Therefore, system efficiency must be determined oncethe system 11 is at steady state (i.e., compressor 10 has run forroughly 10 minutes). The compressor power is determined by measuring thecurrent at 68. The blower and fan power can be measured by similarcurrent sensors and relayed to the processing circuitry 70 and/or thesystem controller.

Once compressor capacity is determined, condensing temperature andambient temperature can used to confirm a high-side or a low-side fault.FIG. 26 shows a graph of condenser temperature difference (TD) versuscapacity. Generally speaking, a fault yielding about 50 percent ofnormal condenser TD is deemed a severe low-side fault, while a faultyielding greater than about 150 percent of normal condenser TD is deemedas sever high-side fault. Such calculations allow the processingcircuitry to further categorize faults and confirm fault determinations.

FIG. 27 provides an additional approach to categorizing a fault aseither a low-side fault or a high-side fault and even allows theprocessing circuitry 70 to declare varying degrees of high-side andlow-side faults. A normal temperature difference (TD) defined generallybetween a TD1 and a TD 2, may have varying degrees of high-side andlow-side faults such as mild high-side faults, severe high-side faults,mild low-side faults, and severe low-side faults. Such categorizationprovides the control system 12 with the ability to allow the compressor10 to operate under certain fault conditions either at full capacity orat a reduced capacity or cease operation all together.

For example, under a mild high-side or low-side fault, the processingcircuitry 70 may allow the compressor 10 to operate in a “limp-along”mode to provide operation of the compressor at a reduced output, whilesome faults, such as a severe high-side or low-side fault require theprocessing circuitry 70 to immediately shut down the compressor 10. Suchoperation adequately protects the compressor 10 while allowing some useof the compressor 10 under less-severe fault conditions.

In addition to stratifying faults based on temperature difference, thecontrol system 12 can also categorize faults (i.e., severe, mild, etc.)based on discharge superheat, as shown in FIG. 28. Discharge superheatis generally referred to as the difference between discharge linetemperature and condenser temperature, as previously discussed. Suchcategorization allows the processing circuitry 70 to similarly allow thecompressor 10 to operate, even at a reduced capacity, when certain faultconditions are present. Such operation adequately protects thecompressor 10 by ceasing operation of the compressor 10 under severeconditions such as floodback and wet suction conditions while currentlyoptimizing output of the compressor 10 by allowing some use of thecompressor 10 under less-severe fault conditions.

In addition to providing information regarding compressor and systemfault information, sensors 66, 68 can also be used during installation.FIG. 29 represents a flowchart detailing an exemplary installation checkof the compressor 10 based on condenser TD and discharge superheat.After installation is complete, the initial efficiency of the compressor10 is determined, as shown in FIG. 22.

At installation, the compressor 10 is charged with refrigerant and isrun for thirty minutes. The processing circuitry 70 is able to determinecondenser temperature, evaporator temperature, discharge superheat, andsuction superheat by monitoring sensor 66, 68, as previously discussed.Such information allows the installer to determine an exact cause of afault at installation such as a fan blockage or an over or under charge,as shown in FIG. 29. For example. If the condenser temperature is abovea predetermined level, an installer would look to see if either thesystem 11 is overcharged or if the condenser fan is blocked. Conversely,if the condenser temperature is below a predetermined level, theinstaller would check the discharge superheat to differentiate betweenan over/under charge and between a blocked evaporator/condenser fan.Therefore, sensors 66, 68 allow the installer to diagnose the compressor10 and system 11 without requiring external gauges and equipment.

FIG. 31 shows that the discharge line temperature can be used inconjunction with the ambient temperature sensor to provide an installerwith an additional diagnostic tool. Specifically, particular temperaturedifferences (i.e., discharge line temperature—ambient temperature)relate to specific fault conditions. Therefore, this temperaturedifference is useful to the installer in properly diagnosing thecompressor 10 and system 11.

FIG. 32 further demonstrates that after the discharge line temperatureis checked at installation, that current measurements can be used tofurther diagnose the compressor 10 and system 11. Specifically, once thedischarge line temperature is known to be satisfactory, the currentreadings taken by sensor 66 can narrow-down additional areas of concern.

As described, the protection and control system 12 uses a single set ofdependent variables (i.e., discharge line temperature and current) toderive a multitude of independent variables (i.e., evaporatortemperature, condenser temperature, and suction superheat). Suchindependent variables are then used by the system 12, in conjunctionwith the dependent variables, to diagnose the compressor 10 and system11 to thereby optimize compressor and system performance.

The description of the present teachings is merely exemplary in natureand, thus, variations that do not depart from the gist of the teachingsare intended to be within the scope of the present teachings. Suchvariations are not to be regarded as a departure from the spirit andscope of the present teachings.

1. A system comprising: a compressor operable in a refrigeration circuitand including a motor; a current sensor providing a high-side signalindicative of an operating condition of a high-pressure side of therefrigeration circuit; a discharge line temperature sensor providing alow-side signal indicative of an operating condition of a low-pressureside of the refrigeration circuit; and processing circuitry processingsaid high-side signal and said low-side signal to indirectly determine anon-measured operating parameter of the refrigeration circuit.
 2. Thesystem of claim 1, wherein said non-measured operating parameter isselected from the group comprising: condenser temperature, evaporatortemperature, suction superheat, and discharge superheat.
 3. The systemof claim 2, wherein said condenser temperature is a function of current.4. The system of claim 2, wherein said evaporator temperature is afunction of said condenser temperature and discharge line temperature.5. The system of claim 2, wherein said discharge superheat is a functionof said condenser temperature and discharge line temperature.
 6. Thesystem of claim 2, wherein said suction superheat is a function of saiddischarge superheat.
 7. The system of claim 2, wherein said processingcircuitry is operable to detect a floodback condition based on acomparison of discharge superheat temperature to a predetermineddischarge superheat temperature.
 8. The system of claim 7, wherein saidpredetermined discharge superheat is approximately equal to fortydegrees Fahrenheit or less.
 9. The system of claim 1, further comprisinga system controller in communication with said processing circuitry. 10.The system of claim 9, wherein said system controller receives saidhigh-side signal and said low-side signal and is operable to verify saidnon-measured operating parameter determined by said processingcircuitry.
 11. The system of claim 9, wherein said system controllerincludes at least one hand-held computer.
 12. The system of claim 11,wherein said hand-held computer is at least one of a personal dataassistant and a cellular telephone.
 13. A method comprising: generatinga high-side signal indicative of high-pressure operating conditions at acompressor in a refrigeration circuit; generating a low-side signalindicative of low-pressure operating conditions at said compressor insaid refrigeration circuit; and processing said high-side signal andsaid low-side signal to indirectly determine a non-measured operatingparameter of said refrigeration circuit.
 14. The method of claim 13,wherein said measuring a high-side signal includes detecting current.15. The method of claim 13, wherein said measuring a low-side signalincludes detecting a discharge line temperature.
 16. The method of claim13, wherein said determining said non-measured operating parameterincludes determining at least one of condenser temperature, evaporatortemperature, suction superheat, and discharge superheat.
 17. The methodof claim 16, further comprising calculating a condenser temperaturedifference and said discharge superheat to diagnose said refrigerationcircuit.
 18. The method of claim 17, wherein said calculating includesderiving an ambient temperature and subtracting said ambient temperaturefrom said condenser temperature.
 19. The method of claim 18, whereinsaid step of deriving includes measuring discharge line temperature atcompressor start-up.
 20. The method of claim 13, further comprisingcommunicating said non-measured operating parameter of saidrefrigeration circuit to a system controller.
 21. The method of claim20, further comprising verifying said non-measured operating parameterof said refrigeration circuit determination at said system controller.22. The method of claim 21, wherein said verifying includes calculatingsaid non-measured operating parameter of said refrigeration circuitbased on said high-side signal and said low-side signal communicated tosaid system controller by said processing circuitry.
 23. The method ofclaim 21, wherein said verifying includes calculating said non-measuredoperating parameter of said refrigeration circuit based on saidhigh-side signal and said low-side signal detected by said systemcontroller.